455Eldorado

Here's something someone might find useful...

I've been looking for a way to make my 1982-85 digital speedometer read speeds above 85Mph without flashing. The cluster is from a 1982-85 Cadillac but many of the GM digital speedometers from early 80's are the same.

The trick is to solder a resistor (or a jump wire, but I prefer a 1k-47k or similar resistor simply to limit current, if any) between pin 31 and GND (or pin 20) on the circuit board with the 40pin, 8022 microcontroller (8022 only). If you have a 8048 microcontroller this will not work.

This will make it read above 85Mph/137Kmh. However, the readout will be incorrect.
Because of the incorrect speed readout I instaled a Dakota Digital SGI-5
calibration module ($80) between the sensor and the cluster.

There's still a minor speed readout discrepancy but only of about 1Mph at lower speeds (up to 20Mph).

djcrook73

i always hated that feature as i had an 86 z24 that did the same thing.. with a 2.8 v6 it did'nt matter all that much but did gm think it would bore people out of wanting to go faster? im assuming you have an 80s eldorado with a 455 which is pretty cool as it must be nice with the extra power. i remember one of the older guys in my neighborhood having a white/ red interior one when i was 13 or so and thinking what a nice design and interior it had and always wanted one.

455Eldorado

The 85Mph speedometer limit for all cars in the US was a government idea to reduce gas consuption/emissions or something to this affect...

I saw once (in 19 years since I bought the car) an export type of Eldorado speedometer with no 85mph limit, but it was analog. I guess there are some digital "export" cluster out there as well...but I never saw one. I bought a canadian model on Ebay once, with odometer in "kilos" but the flashing is also present.

kartmaster

I could count on one hand the number of times my Toronado has been going 85+, haha. I really do drive like a Grandpa and my wife consistently reminds me so.

Cool mod though!

jpc647

Not an oldsmobile, but I want to share. My 88 thunderbird had a feature like this as well in the digital dash where it stopped at 85. Even with a tired v6, it would still go faster, but no readout more than 85. I too had to solder a jumper wire between two of the pins for the speedometer to read higher.

I never checked accuracy at 85+, I didn't care all that much, just wanted to see if it would work.

455Eldorado

Thuderbird has dedicated connections on the circuit board that will do the trick if jumper wired...so I've heard. I believe the accuracy is not a problem with your '88 T-Bird
GMs don't have this option. The difference between the accual speed and what the cluster reads would be 15-20Mph or so without the interface...

ThePackRat

Sounds like a cool ride.

Love those 79-85 E-Bodies.

I've only owned Toro's in the past (81 & 85) ..... but would love to have (1) of each E-Body one day.

My 1985 was analog ... but it didn't see much time past that 85 mph limit.
(considering how loooooong it would take to get it there)

The 81 (only available w/analog 79-83) on the other hand w/a rebuilt 350 would do so quite regularly & could easily bury the speedo & put a smile on your face doing so.

It was confirmed that car could easily do at least 120 ... much to the frustration of those that underestimated its abilities (which most did).

455Eldorado

In a garage, with the signal generator connected to the cluster...just to show the "above 85Mph" readout
In reality, I'd go up to about 100Mph (cruise) and still be comfortable with the ride. But if the suspension and steering was
any stiffer it could go much faster...